EVALUATION OF IRRIGATED COTTON CULTIVARS IN SOUTH AFRICA.
by
M. M. PRETORIUS
Submitted in fulfilment of the requirements for the degree of
Magister Scientiae Agriculturae
Department of Soil, Crop and Climate Sciences Faculty of Natural and Agricultural Sciences
University of the Free State BLOEMFONTEIN.
November 2009
TABLE OF CONTENTS
DECLARATION……….……….… iii
ACKNOWLEDGEMENT………..……….. iv
ABSTRACT……….……….……... v
LIST OF TABLES………...……….…………... vi
LIST OF FIGURES……….……. viii
CHAPTER 1 INTRODUCTION ……….….. 9 CHAPTER 2 L LITERATURE STUDY………...……….. 12 2.1 History of cotton……….……… 12 2.2 Botany of cotton……….……….…….….. 13 2.3 Uses of cotton……….………..….. 16 2.4 World situation……..……….….……... 17
2.5 Production of cotton in South Africa……...………..……….….. 19
2.6 Soil and climatic requirements…………..……….……….…... 20
2.7 Production areas.………..……….……….…… 22
2.8 Production practices………...……….……….….. 24
2.9 Planting method……….….… 25
2.10 Weed control……….……... 26
2.11 Harvesting……….………... 27
2.12 Quality and grading…………..……….………..……. 28
2.13 Factors affecting yield and quality of cotton……….………... 29
2.14 Breeding……….……….…. 33
CHAPTER 3 MATERIALS AND METHODS…..……..……….……… 36
3.1 Trial sites………..………….……….……….……... 36
3.2 General trial procedure………..……….……….………... 36
3.3 Fertilization...……….……….………... 38
3.4 Irrigation…..…….……….……….…… 39
3.5 Weed control...……….…...……….…..……….… 39
3.6 Insect control………...……….……….………. 40
3.7 Harvesting and measurements……….……….……….………. 40
CHAPTER 4 LOCALITY ANALYSIS……….……….………... 50 4.1 Introduction……….……….……….……….…… 50 4.2 Loskop……….……….………..……… 50 4.3 Makhathini……….……….………...………. 54 4.4 Rustenburg……….……….…………...………. 57 4.5 Upington……….……….……..………. 61 4.6 Vaalharts……….………....……… 63 4.7 Weipe……….………...……….………. 67 CHAPTER 5 CULTIVAR ADAPTABILITY……….……... 71
5.1 The AMMI model……….……….……… 71
5.2 Research procedure……….……….………..……… 72
5.3 Seed cotton yield (kg ha-1)………….……….….………... 73
5.4 Fibre percentage (%)……….……….……… 75
5.5 Fibre yield (kg ha-1)……….………...………...….… 77
5.6 Fibre length (mm)……….……….………….… 79
5.7 Fibre strength (g tex-1)……….………...… 81
5.8 Micronaire……….……….……… 83
CHAPTER 6 DISCUSSION AND RECOMMENDATIONS..……….……… 86
6.1 Introduction……….………...…… 86
6.2 Seed cotton yield (t ha-1)……….………….….... 86
6.3 Fibre percentage (%)……….……….….... 87
6.4 Fibre yield (t ha-1)………...……….……..….. 87
6.5 Fibre length (mm)………..…. 91
6.6 Fibre strength (g tex-1)……….………... 91
6.7 Micronaire……….………. 91 6.8 Final recommendation……… 95 REFERENCES………...……….………. 96 Addendum 1………..……….……….. 103 Addendum 2……….……… 107 Summary……….……….. 109 Opsomming……….………. 110
DECLARATION
I declare that this dissertation is my own unaided work. It is being submitted for the degree of M.Sc (Agric) in the Faculty of Natural and Agricultural Sciences, University of the Free State, Bloemfontein, RSA. It has not been submitted before
for any degree or examination in any other University.
ACKNOWLEDGEMENT
I express my thanks to the following institutions and advisors whose assistance led to the successful completion of this study:
The Agricultural Research Council (ARC) for the bursary, which enabled me to pursue this study. The ARC-Institute for Industrial Crops (ARC-IIC) for the use of their facilities. The following people for their inputs which enabled me to complete this work: Mr Jurie Steyn (Makhathini Experimental Farm), the late Dr Chris Theron (Upington Experimental Farm), Mr Johan van Schalkwyk (Vaalharts Experimental Farm), Miss Coleen Fourie (Loskop Experimental Farm, and Mr Jacques Willemse (Hanaline Farm, Weipe) for the execution of the trials and the collection of the data. Miss Alfreda Pohl and Mrs Karen Smook for editing the manuscript.
The previous head of the Agronomy section at the ARC-IIC, Dr Dippenaar, for his constant encouragement and belief in my abilities. During his years as sectional head, he was an excellent mentor.
Marie Smith and Elise Robbertse are thanked for their assistance with the statistical analyses of the study.
My study leaders, Dr J Allemann and Dr L Owoeye for their guidance.
Last but not least, my sincere thanks to my children, Jan-Paul Pretorius and the late Wesley Venables, for their support, which allowed me to complete this work. They are also thanked for their patience during the long periods of absence when I was planting, visiting and harvesting the National Cotton Cultivar Trials.
ABSTRACT
Cotton (Gossypium hirsutum) is a globally important fibre crop. The cottonseed has a high oil and protein content and is used for human and animal consumption. Innumerable commodities are made from cotton. Annual cultivar evaluations are essential to compare the yield and quality obtained in different production areas, to obtain experimental data to recommend the most suitable cultivar for a production area. The objective of this study was to evaluate the performance of different cotton cultivars under irrigation in South Africa. The cultivars planted from the 2003/2004 season up to the 2005/2006 season were NuOPAL, DeltaOPAL, DeltaOpal RR, LS9219 and SZ9314. The localities were Loskop (Mpumalanga Province), Makhathini (KwaZulu-Natal), Rustenburg (North-West Province), Vaalharts and Upington (Northern Cape) and Weipe (Limpopo Province). The Additive Main Effects and Multiplicative Interaction (AMMI) statistical model was used to describe the effect of cultivar x environment interaction on the yield of cotton planted under irrigated conditions. It is recommended that cotton producers should plant NuOPAL, since it was selected by the AMMI model as the best performer in respect of seed cotton yield and fibre yield (kg ha-1) in fifteen out of eighteen environments.
LIST OF TABLES
Table 2.1 World cotton area, yield, production, imports, consumption and exports……… 18
Table 2.2 Areas planted and yield in the Republic of South Africa………. 20
Table 3.1 The different amounts of nutrients required by the aboveground parts of the cotton plant for the Production of different yields……….. 38
Table 3.2 Soil form, fertilization amounts and rainfall during different seasons at different localities……….. 39
Table 3.3 Herbicides used to control weeds at the various trial sites……….……… 40
Table 3.4 Control thresholds for important cotton pests………...… 42
Table 3.5 Soil analysis during the 2003 to 2006 seasons at Loskop………. 43
Table 3.6 Insect control during the 2003 to 2006 seasons at Loskop………...… 44
Table 3.7 Soil analysis during the 2003 to 2006 seasons at Makhathini……….. 45
Table 3.8 Insect control during the 2003 to 2006 seasons at Makhathini………. 45
Table 3.9 Soil analysis during the 2003 to 2006 seasons at Rustenburg……….. 46
Table 3.10 Insect control during the 2003 to 2006 seasons at Rustenburg………. 46
Table 3.11 Soil analysis during the 2003 to 2006 seasons at Upington……….…. 47
Table 3.12 Insect control during the 2003 to 2006 seasons at Upington……… 47
Table 3.13 Soil analysis during the 2003 to 2006 seasons at Vaalharts………. 48
Table 3.14 Insect control during the 2003 to 2006 seasons at Vaalharts……… 48
Table 3.15 Soil analysis during the 2003 to 2006 seasons at Weipe……….. 49
Table 3.16 Insect control during the 2003 to 2006 seasons at Weipe………. 49
Table 4.1 Yield data for the various cotton cultivars, planted at Loskop during the 2003 to 2006 seasons……. 51
Table 4.2 Quality data for the cotton cultivars, planted at Loskop during the 2003 to 2006 seasons………….. 53
Table 4.3 Yield data for the various cotton cultivars, planted at Makhathini during the 2003 to 2006 seasons.. 55
Table 4.4 Quality data for the cotton cultivars, planted at Makhathini during the 2003 to 2006 seasons……… 57
Table 4.5 Yield data for the various cotton cultivars, planted at Rustenburg during the 2003 to 2006 seasons.. 58
Table 4.6 Quality data for the cotton cultivars, planted at Rustenburg during the 2003 to 2006 seasons……… 60
Table 4.7 Yield data for the various cotton cultivars, planted at Upington during the 2003 to 2006 seasons….. 62
Table 4.8 Quality data for the cotton cultivars, planted at Upington during the 2003 to 2006 seasons………... 63
Table 4.9 Yield data for the various cotton cultivars, planted at Vaalharts during the 2003 to 2006 seasons…. 65 Table 4.10 Quality data for the cotton cultivars, planted at Vaalharts during the 2003 to 2006 seasons………... 66
Table 4.11 Yield data for the various cotton cultivars, planted at Weipe during the 2003 to 2006 seasons…….. 68
Table 4.12 Quality data for the cotton cultivars, planted at Weipe during the 2003 to 2006 seasons……… 69
Table 5.1 Summary of the mean seed cotton yields and Genotypic IPCA scores……… 74
Table 5.2 Summary of the mean seed cotton yields and Environmental IPCA scores………. 74
Table 5.3 Summary of the mean fibre percentages and Genotypic IPCA scores………..………... 76
Table 5.4 Summary of the mean fibre percentages and Environmental IPCA scores……….. 76
Table 5.6 Summary of the mean fibre yields and Environmental IPCA scores………... 78
Table 5.7 Summary of the mean fibre lengths and Genotypic IPCA scores……….……… 80
Table 5.8 Summary of the mean fibre lengths and Environmental IPCA scores………..………... 80
Table 5.9 Summary of the mean fibre strengths and Genotypic IPCA scores…………...………... 82
Table 5.10 Summary of the mean fibre strengths and Environmental IPCA scores………..……...…………..… 82
Table 5.11 Summary of the mean fibre micronaire and Genotypic IPCA scores………... 84
Table 5.12 Summary of the mean fibre micronaire and Environmental IPCA scores……… 84
Table 6.1 AMMI model’s best three cultivar selections for mean seed cotton yield (t ha-1)……….……...…… 88
Table 6.2 AMMI model’s best three cultivar selections for mean fibre percentage (%)……….. 89
Table 6.3 AMMI model’s best three cultivar selections for mean fibre yield (t ha-1)……….. 90
Table 6.4 AMMI model’s best three cultivar selections for mean fibre length (mm)…...…..………. 92
Table 6.5 AMMI model’s best three cultivar selections for mean fibre strength (g tex-1)...…………....……… 93
Table 6.6 AMMI model’s best three cultivar selections for mean micronaire...……….. 94
ADDENDUM 1 Table 1 The analysis of variance table (ANOVA), for seed cotton yield (kg ha-1)………... 104
Table 2 The analysis of variance table (ANOVA), for fibre percentage (%).………... 104
Table 3 The analysis of variance table (ANOVA), for fibre yield (kg ha-1)………..………...………. 105
Table 4 The analysis of variance table (ANOVA), for fibre length (mm)….………..……….…. 105
Table 5 The analysis of variance table (ANOVA), for strength (g tex-1)..………... 106
LIST OF FIGURES
Figure 2.1 Morphology of the cotton plant……… 15
Figure 2.2 Fruit formation of the cotton plant………... 16
Figure 2.3 Uses of cotton………... 19
Figure 2.4 Cotton-production areas of the republic of South-Africa………..…...………… 23
Figure 2.5 Crop factors for cotton in different climatic regions……….……....… 27
Figure 3.1 Localities in the different irrigated cotton-production areas in South Africa showing trial sites….……... 37
Figure 5.1 AMMI model 2 bi-plot for five cotton cultivars and 18 environments for the duration 2003 to 2006, seed cotton yield (kg ha-1)………..…….……….………….… 75
Figure 5.2 AMMI model 2 bi-plot for five cotton cultivars and 18 environments for the duration 2003 to 2006, fibre percentage (%)…….………..…….……….….… 77
Figure 5.3 AMMI model 2 bi-plot for five cotton cultivars and 18 environments for the duration 2003 to 2006, fibre yield (kg ha-1)………..…….………..………... 79
Figure 5.4 AMMI model 2 bi-plot for five cotton cultivars and 18 environments for the duration 2003 to 2006, fibre length (mm)……….………..…….……….…….. 81
Figure 5.5 AMMI model 2 bi-plot for five cotton cultivars and 18 environments for the duration 2003 to 2006, fibre strength (g tex-1)….………..…….……….……….….. 83
Figure 5.6 AMMI model 2 bi-plot for five cotton cultivars and 18 environments for the duration 2003 to 2006, micronaire………..…….……….…..… 85
ADDENDUM 2 Figure 1 Example of the AMMI’s classification of the adaptability and stability characteristics of sorghum cultivars……….… 109
CHAPTER 1
INTRODUCTION
Upland cotton (Gossypium hirsutum L.), a member of the Malvaceae family, is believed to have originated in tropical America (Purseglove, 1974). It is considered to be the most important textile fibre crop in the world (Zumba, 2004), providing roughly half of the global fibre requirement (Myers and Stolton, 1999). Fibre from various species within this genus has been used for several thousand years to produce clothing and other textiles in places such as India, the Nile valley and Peru (Myers and Stolton, 1999). Cotton has long been valued in the clothing industry because of the comfort of clothing produced from its fibre (Orr, 1977).
Cotton is regarded as one of the most versatile agricultural products in the world and is used in the manufacture of more than 1 000 major products (Broodryk, 1997). It has been viewed as the world’s most important cash crop for many years (Cantrell et
al, 2003). Not only is the fibre important, but the seed is also of economic
importance, because it is used for planting and as an oilseed (Broodryk, 1997). After soya bean, cotton is the second most important oilseed crop in the world (Zumba, 2004). Edible oil is produced by pressing the seed to extract the oil, and removing the toxic compound, gossypol, during the refining process (Cotton SA, 2008). The resulting oilcake is also an important source of protein in the animal feed industry (Purseglove, 1974).
In South Africa cotton is an important crop because of its agricultural value and potential to create employment. The fibre has a variety of uses in the textile industry and is also used in the armament industry (Le Roux, 1988). Cotton has been produced in this country since 1846, although large-scale production virtually ceased after 1870 (CottonSA, 2008). From a small planting of 12 to 14 ha in 1904, the cotton industry expanded to become an important agricultural industry in South
Africa, with plantings of close on 100 000 ha in the 1999/2000 season (CottonSA, 2008).
The total area planted to dry land cotton has steadily decreased from a high of 69 578 ha in the 1998/99 season to 2 863 ha in the 2007/08 season, while at the same time the average yield of seed cotton has decreased from 580 to 541 kg ha-1. Production under irrigation has shown a similar decrease (20 361 to 7 700 ha), but yields have steadily increased from 2720 to 3640 kg ha-1 over the same period (CottonSA, 2008). This decrease in cotton production is related to the poor price of South African cotton on the international market. The low price results in a decrease in income for both small-scale and commercial producers and makes other cash crops more attractive (Bruwer, 2007).
The increase in yield in the RSA can be ascribed to the cotton-breeding programme that has evolved over the past 77 years. This evolution has resulted in four distinct breeding programmes located in the Upington, Vaalharts, Loskop and Rustenburg production areas. Each of these programmes has its own objective, based on the specific potential and agricultural situation encountered in that specific area (Greeff, 1986).
Leafhoppers or jassids (Jacobiella fascialis) can cause considerable damage to cotton foliage, while Verticillium wilt also causes economic losses. Jassid-resistant lines (Cornelissen, 2002) and Verticillium-tolerant lines (Theron, 2007) have been evaluated in the breeding programme of the Agricultural Research Council – Institute for Industrial Crops, in order to find high-yielding cultivars tolerant to these two pests. The use of such cultivars will contribute to increased profitability. The introduction of transgenic cotton in the USA in 1995 brought significant changes to the cotton industry. Resistance to bollworm and the herbicide glyphosate was introduced and production costs were thereby significantly reduced (Jordan et al, 2003). Consequently, the number of transgenic cotton varieties planted as well as the
area planted to transgenic cotton throughout the cotton-producing countries of the world has increased significantly (Jordan et al, 2003).
The correct choice of cultivar is very important in cotton production as this contributes to the reduction of risk while optimizing yield and quality, which in turn affects income. A wide range of cultivars are presently available on the international market and also in the RSA, all of which differ regarding their adaptability, yield potential, agronomic characteristics and disease susceptibility. It is important that producers should be aware of both the superior and poor characteristics of each cultivar so that this genetic diversity can be fully utilized throughout the wide range of agro-ecologies found in South Africa.
To enable breeders and agronomists to make good recommendations, it is also imperative that they continually evaluate both current and newly developed cultivars, as well as newly imported cultivars that were bred in other countries, for their adaptability under both dry land and irrigated conditions in the various production areas found in South Africa. Furthermore, it is important to import or breed cultivars with a short growing season, since several cotton-production areas in the Republic of South Africa are subject to shorter growing seasons due to temperatures, availability of moisture and crop rotation.
The aim of this study was to evaluate the performance of different cultivars under irrigation in South Africa.
CHAPTER 2
LITERATURE STUDY
2.1 History of cotton
2.1.1 Origin and species
Cotton has been cultivated since prehistoric times and was used as clothing in Brazil, Peru and Mexico long before the discovery of America by Europeans (Poehlman, 1987). Cotton plants originated as tropical scrubs and developed through the ages to become the source of the most important textile fibre. Archaeological discoveries showed that cotton was in use in western Pakistan as early as 3000 B.C. (Anonymous, 1979)
Cotton belongs to the genus Gossypium of which four of the 43 Gossypium species are considered to be of major agricultural importance. They produce spinnable lint that is of great value to the spinning and textile industries (Areke, 1999). Cultivated cotton species are important in that they produce fibres that are spinnable whereas wild relatives produce seeds without fibres, or very short fibres. However, wild relatives are also useful in that they contribute some useful traits for the improvement of cultivated cultivars (Meredith et al, 1996). Worldwide all cotton produced belongs to one of the following four species Gossypium hirsutum L., G. barbadence L., G.
herbaceum L., and G. arboreum L. More than 90 % of all cotton produced is Gossypium hirsutum L. (Kaynak, 2007)
In 1516, Portuguese explorers in South Africa came across natives who had planted and used cotton for making garments (Scherffius & Oosthuizen, 1924). Cotton was planted in the Western Cape as early as 1690 and was reintroduced in 1846 by Dr Adams of the American Mission (van Heerden, 1988a). Cotton was planted on a
large scale in KwaZulu-Natal and the Cape colony during 1860 to 1870 due to increased demand as a result of the American Civil War (de Kock, 1994).
A cotton gin was erected in the Tzaneen area, where cotton was ginned and baled mechanically. The co-operative movement with regard to cotton had its origins in 1922 when a co-operative and ginnery was established at Barberton. By 1969 about 80% of the total crop was being produced in the irrigation areas of Loskop, Vaalharts and Upington (Anonymous, 1979).
2.2 Botany of Cotton
2.2.1 Taxonomy
The botanical classification of cotton according to de Kock (1994), is as follows: Division : Angiospermae Class : Dicotyledonae Subclass : Dilleniidae Order : Malvales Family : Malvaceae Tribe : Gossypieae Genus : Gossypium
According to the classification of Wolfe & Kipps (1959), cotton belongs to the family Malvaceae. There are eight commonly recognized species of cotton, namely:
1 Gossypium barbadense, the long-staple Barbadoes, Sea Island, Egyptian, and
Peruvian varieties.
2 Gossypium herbaceum, the varieties of India, Thailand, China, and Italy.
3 Gossypium hirsutum, the American Upland varieties.
4 Gossypium arboreum, found in Ceylon, Arabia, and South America.
6 Gossypium purpurascens, found widely distributed on islands in the Atlantic,
Indian, and Pacific Oceans.
7 Gossypium braziliense, found in Brazil and other parts of South America.
Perennial shrub or small tree.
8 Gossypium nanking, Chinese or Thailand cotton.
2.2.2 Morphology
Rehm & Espig (1991) stated that all cotton species are potentially perennial, even though they are normally grown for only one year in modern agriculture. The cotton seedling, with its fast-growing radicle and gland-studded stem (hypocotyls), which lifts the two big cotyledons and the growing point out of the soil, develops from the seed (van Heerden, 1978). Cotton plants form a strong taproot, which develops even at the seedling stage, and which can reach a depth of 3 m (Rehm & Espig, 1991). A cotton plant has a single ascending main stem that bears a leaf at each node and usually has one branch. Vegetative branches (monopodia) tend to be produced lower down on the plant, while reproductive (sympodia) branches are produced higher up or on the monopodia (Figure 2.1). Sympodia are generally short and terminate in a flower bud (Bennett, 1991).
Cotton leaves are large, palmately lobed (three, five or seven lobed) and covered with multicellular stellate hairs (Kochhar, 1981). Plants in the genus Gossypium have showy flowers, each with five sepals united into a cuplike calyx and five petals of whitish or yellowish color that often turn pink with age (Wolfe & Kipps, 1959). Pollination usually occurs in the early afternoon. By late afternoon the corolla begins to change colour, first becoming a faint pink and later a deep red-mauve. At the same time, the bracts (calyx) close around the ovary. At this stage, the bud is termed a square. As the square develops, the fruit increases in size and protrudes beyond the bracts. The fruit or boll is a 3 to 5-locular, dehiscent capsule, each locule containing
approximately nine seeds (Figure 2.2). These seeds produce the lint fibres as well as the short fuzz (Bennett, 1991).
Figure 2.1. Morphology of the cotton plant (Bennett, 1991) a - square
b - burst boll c - sympodium d - monopodium e - main stem
Figure 2.2 Fruit formation: a. Flower bud; b. Flowers; c. Unripe boll; d. Mature boll Cotton fibres represent epidermal prolongations of seed coat cells. Differentiation of such hairy growths occurs on the epidermal surface of ovules even before pollination, but proceeds quite rapidly after pollination, reaching maturity in 45 to 50 days. The fibres reach their full length during the first twenty-five days of boll development, after which they start to increase in thickness (Kochhar, 1981).
2.3 Uses of cotton
The first step in the processing of the cotton picking is taken at the gin, where the fibre, about 36 % of the mass, is separated from the seed. The fibre, which is the most important product, consists mainly of cellulose. The various products derived from cotton are illustrated in Figure 2.3 (Schröder, 1990a). Cotton lint is the most important vegetable fibre in the world today and is woven into fabrics, either alone or
combined with other fibres (Purseglove, 1974). Cotton is used as an input in more than fifty industrial sectors from the textile, food, and film industries to the war industry. Cotton production has changed considerably to keep pace with the increases in world population and the socio-economic needs of societies (Kaynak, 2007).
2.3.1 Fibre
Lint is the most important industrial raw material for which cotton is widely cultivated (Areke, 1999). Cotton fibre serves for approximately half of all domestic textile uses. Cotton has unique basic qualities, which accounts for it being the leading fibre in terms of quantities consumed (Berger, 1969).
2.3.2 Seed
According to de Kock (1994) cottonseed production and processing ranks second among the five major oilseeds in the world market (soybean, cotton, sunflower, peanut and rape). Oil can be extracted from cottonseed and purified into edible oil or used in the processing of products such as soap, cosmetics, pharmaceuticals, lubricants and also culinary products (Areke, 1999). Cotton seed oil is one of the most important of the world’s semi-drying oils and is primarily a food product, used in making cooking and salad oil, mayonnaise, margarine and various other products (Berger, 1969).
2.4 World situation.
Cotton is ranked high among the world’s economically important crops. This is due to the numerous products that are processed from cotton, as well as the ever- increasing demand for such products (Areke, 1999).
Cotton plays an important role in everyday life and is of economic importance. Certain factors, such as the increasing population, the demand for natural fibre, and the improvement in the quality of life, have led to higher demand for cotton fibre. Only a limited number of countries are suitable for cotton production and 80 % of the cotton in the world is produced in China, the USA, India, Pakistan, Uzbekistan, Brazil, and Turkey. The world cotton area, yield, production, imports, consumption and exports are presented in Table 2.1 (ICAC, 2006).
Table 2.1 World cotton area, yield, production, imports, consumption and exports (ICAC, 2006)
Marketing year Area (1000ha) Yield (kg ha-1) Production (Mt) Imports (MR) Consumption (Mt) Exports (Mt) 1995/1996 36.1 564 20.3 5.805 18.4 6.0 1996/1997 34.1 575 19.6 6.134 19.0 6.0 1997/1998 33.8 594 20.1 5.756 19.0 6.0 1998/1999 32.8 569 18.7 5.405 18.5 5.5 1999/2000 32.1 595 19.1 6.068 19.6 6.1 2000/2001 31.8 612 19.5 5.755 19.9 5.9 2001/2002 33.4 644 21.5 6.195 20.1 6.4 2002/2003 29.9 646 19.3 6.586 20.9 6.6 2003/2004 32.1 645 20.7 7.261 21.3 7.2 2004/2005 35.2 747 26.3 7.326 23.4 7.8
2.4.1 Production and consumption
The latest estimates from the International Cotton Advisory Committee (ICAC), showed that 23.7 million tons of cotton was produced during 2008/2009, compared with 26.2 million tons in 2007/2008. This decrease in production is contributed to decreasing cotton returns, more attractive prices for competing crops, and difficulties in financing inputs (ICAC, 2009).
SEED PULP Cake and meal - Flour - bread, cake, biscuits - Feed - Cattle and sheep - Fertilizer
Crude oil - Refined oil - salad and cooking oil, mayonnaise, margarine
Sediment oil - Soap
- Glycerine, explosives, pharmaceuticals, cosmetics - Fatty acids - rubber, plastics, insecticides, fungicides HULLS Feed for beef and dairy cattle
Fertilizer - mulch Bran - livestock feed Furfural - synthetic rubber
SEED
COTTON
Pulp - Viscose, Cellulose nitrate, Paper SEED
COTTON
Absorbent cotton
LINTERS Yarn - Lamp and candle wick, twine, rugs
Felts - Automotive upholstery, pads, cushions, mattresses
PLANTING
PURPOSES
LINT CLOTHING Clothes, underwear, gloves, mackintoshes, etc
Linings for tyres, bags, rope, tents, medical bandages, etc Sheets, towels, bedspreads, curtains
Figure 2.3. Uses of cotton (Schröder, 1990a)
2.5 Production of cotton in South Africa
Cotton production in South Africa provides employment for 100 000 people. In 2003, the textile industry’s local sales fetched R12.4 billion (a further R13 billion was obtained from the sale of garments/textile) and exports totaled R3.8 billion (Anonymous, 2005)
South African cotton is produced under both irrigated and dry land conditions. The second estimate for the 2008/2009 production year shows a total cotton harvest of 42 042 bales of fibre (Cotton SA, 2008). The estimated harvest will be the smallest in 40 years. This is mainly due to the perception that cotton farming is no longer a viable option, especially in the light of the favourable prices of other competitive summer crops. Cotton is getting strong competition from other crops, such as maize and sunflower, whose prices skyrocketed. These crops not only give farmers higher prices, but also need lower inputs (Cotton SA, 2008). Table 2.2 shows the hectares planted and yield for South Africa.
2.6 Soil and climatic requirements
2.6.1 Soil
Cotton is grown on a large variety of soils, but it does best on a deep, crumbly soil with a good humus supply and favourable moisture-holding capacity. Sandy loams, loams and well-granulated clay loams are considered best, with optimum pH ranges of between 5.2 and 7 (Berger 1969). Cotton grows well on moderately fertile soils. Soils in the cotton regions range from sands to very heavy clays with acidity levels ranging from pH 5.2 to pH 8+ (Martin & Leonard, 1976).
Table 2.2 Areas planted and yield in the Republic of South Africa (Cotton SA, 2008)
Marketing year Irrigation (ha) Dry land (ha) Total (ha) Yield (Kg ha-1)
Irrigation Dryland Average
1997/98 15954 67017 82971 2189 403 746 1998/99 20361 69578 89939 2724 580 1065 1999/00 31263 67356 98619 2680 545 1222 2000/01 10486 40282 50768 3107 777 1258 2001/02 18539 38153 56692 3455 593 1529 2002/03 9791 28897 38688 3538 515 1280 2003/04 10322 12252 22574 3482 475 1850 2004/05 18269 17450 35719 3455 492 2007 2005/06 12897 8866 21763 3791 521 2459 2006/07 9720 8394 18114 3633 485 2174 2007/08** 7920 3443 11363 3700 541 2844 * Seed cotton
2.6.2 Climate
Kochhar (1981) describes that cotton is essentially a tropical crop, but its cultivation now extends from 37° N to 32° S in the New World and from 47° N in the Ukraine to 30° S in the Old World. Martin & Leonard (1976) explains that climatic conditions are favorable for cotton production where summer temperatures are not lower than 25°C. The cotton-production zone lies between 37° north and 32° south latitude, except in the Russian Ukraine, where cotton is grown at up to 47° north latitude.
2.6.3 Temperature
Cotton needs warm days and relatively warm nights for ideal growth and development (Greeff, 1988). Cotton is a long-season plant, requiring a minimum of 180 to 200 frost-free days, as well as uniformly high temperatures during the growing season (Berger, 1969). Martin, (1976), describes three climatic essentials for cotton cultivation are freedom from frost for a minimum growing and ripening season, an adequate supply of moisture, and abundant sunshine. Cotton requires high temperatures, abundant sunshine, low humidity, especially during picking time, and a long frost-free growing season of about seven months for optimum development (Serfontein 1970).
2.6.4 Light
Abundant sunlight is essential for normal growth processes of cotton plants, because large quantities of carbohydrates have to be building up before cotton plants reached picking maturity. Sufficient sunlight during the long period of boll formation is essential, as long periods of cloudy weather can cause abscission (van Heerden, 1978). Adequate sunshine is important during periods of early growth and full bloom for the proper development of cotton plants. Insufficient sunshine will prevent ripening of the boll to full maturity (Berger, 1969).
2.7 Production areas
Cornish-Bowden (1979) explains that the ideal cotton areas are the irrigated Upington/Prieska areas in the West, the hot Limpopo/Letaba valleys in the North, the Eastern Lowveld areas running down the Mozambique boundary into the Swaziland Lowveld and Northern Natal’s low lying country. Despite certain climatically limitations, cotton has moved out of the classical areas into other areas. The most notable examples of such areas are the Loskop/Rust-de-Winter irrigation areas and the Northern Cape irrigation area of Douglas, Vaalharts and Modderriver.
Ehlers & van Heerden (1976) cited by Dippenaar (1988) drew charts describing the then existing plus potential new cotton-production areas of South Africa. Three temperature areas were described, namely:
a) Favourable areas where both day and night temperatures are optimal from December to February.
b) Less favourable areas where either day or night temperature is optimum for the growth of cotton.
c) Marginal areas where both temperatures are too low for optimal growth.
Although the three cotton areas depicted on the charts have 200 frost free-days per season, it is impossible to deduce the length of the active flower and boll set periods or the main limiting climate factor from the charts. The intermittent sharp decline in night temperatures in the Central Transvaal and the cotton areas in the Northern Cape is a limiting factor that is detrimental to cotton production and fibre quality during some seasons (Dippenaar, 1988).
In South Africa, the Lowveld, central Transvaal and areas further north are usually warm enough in early spring to ensure emergence and good stands. In Griqualand West early season temperatures, until the end of October, are too low for rapid growth of cotton. Increases in minimum air temperature during early spring are more pronounced in the cooler cotton areas than in the warm Lowveld. Early planting of
cotton is therefore recommended in most areas to make the best use of the available growing season (Dippenaar & Human, 1991). Only 1600 to 1900 DGb (available degree days) are available to set a crop potential in the central Transvaal, western Transvaal-Vryburg area and Griqualand West. On the contrary, more than 2400 to 3000 DGb are available to produce a yield in the Lowveld and Limpopo Valley (Dippenaar & Human, 1992).
Cotton production takes place in all the different provinces of South Africa, whereof only the Limpopo Province, Mpumalanga, the Northern Cape and Kwa-Zulu Natal, and to a lesser extend the North West Province is known as cotton production regions. These regions are illustrated in Figure 2.4 (Bennett-Nel, 2007).
2.8 Production practices
2.8.1 Seedbed
The purpose of primary cultivations is to aerate the seedbed, improve penetration of irrigation and incorporate large quantities of plant residues in the soil. The soil water status should be favorable for efficient and cost effective cultivation. Soil that is too wet or too dry when cultivation takes place may result in breaking of the soil structure. Moldboard ploughs should be used with caution since they require high tractive power and can cause a plough sole in certain soils. Chisel implements are just as effective for primary cultivation (ARC, 2004).
2.8.2 Fertilization
2.8.2.1 Nitrogen
Nitrogen has the greatest influence on yield. Cotton requires 112 kg N ha-1 for a 4-ton crop. This implies an application of 140 kg N ha-1 if the efficiency factor of 80% for a sandy soil is taken into consideration. Fertilizer applications must be complemented by good irrigation to keep the effective soil in the 0,9 m deep root zone at field capacity. Sandy soils that are inclined to leach should receive split applications of nitrogen. Half of the N can be applied at planting, with the second application at 7 to 8 weeks after planting (FSSA, 1989). Rochester et al, (1998) stated that irrigated cotton requires up to 200 kg nitrogen N ha-1 to achieve maximum yield.
2.8.2.2 Phosphate
Phosphate fertilization will stimulate more even boll splitting, and also improve fibre quality. The P (Bray 1) in the top 30 cm of soil should be 20 to 30 mg P kg-1. On the
slightly alkaline soils often associated with irrigation areas, the efficiency factor on a build-up soil (20 to 30mg P/kg) may be as high as 80% (FSSA, 1989).
2.8.2.3 Potassium
Potassium plays an important role in respiration, protein synthesis and carbohydrate metabolism. No potassium is normally applied when soils have concentrations of higher than 80, 100 and 120 mg K kg-1 respectively for sand, loam and clay soils (ARC, 2004). Potassium uptake can be prevented or decreased by poorly aerated soil, compaction layers, or a high calcium or magnesium content of irrigated soils (FSSA, 1989).
2.9 Planting method
Various mechanical planters are available in South Africa for cotton planting. Precision planters which space seeds in groups of three to four at desired intra-row spacing are also on the market. Planting to stand is only advisable under conditions that are extremely favorable for germination. Plant the seed about 20 mm deep in clayey soil, or to a maximum of 30 mm in sandy soil for the development of a strong, healthy seedling (ARC, 2004).
2.9.1 Planting date
Soil temperature is one of the most important factors determining planting time. Cotton should not be planted before the topsoil has maintained a temperature of 16 to 18°C or higher for approximately 10 successive days. The second half of October to mid-November can be considered the best time to plant cotton in all the cotton-production areas (ARC, 2004).
2.9.2 Plant spacing and density
Plant populations of approximately 70 000 plants ha-1 under irrigated conditions and 30 000 plants ha-1 under dry land conditions, are recommended. Plant populations
can also be manipulated to reduce the detrimental effect of a very late planting date. Under these circumstances a high plant population with a resulting competition effect forces the plants to grow faster and achieve higher yields (ARC, 2004).
2.9.3 Irrigation
Van Heerden (1964) states that 635 mm of irrigation is adequate for cotton to obtain maximum yield. The topsoil must contain sufficient water for the germination of cottonseeds. Soils should be at field capacity to a depth of at least 100 cm at planting time. A light irrigation (15 to 20 mm) immediately after planting is sufficient to replenish the soil water and ensure good contact between the seed and the soil. Applications of 20 to 25 mm of irrigation per week are usually sufficient. Cotton develops a full leaf canopy between 80 to 100 days after planting. At this stage the water consumption of cotton plants is equal to the evaporation, as measured by the American A-pan, of water from an open surface of water. This stage also coincides with the peaks of flowering and boll setting. Cotton is very sensitive to water stress at this stage (ARC, 2004).
Crop factors for the various cotton producing areas change during the course of the growing season (Figure 2.5). The rate at which the crop factor increases is closely related to the growth rate of the cotton plant (Dippenaar, 1990b). A bigger crop factor is reached much sooner in very hot areas than in the more temperate regions due to the faster growth rates achieved under these conditions. The largest leaf area is also found when the crop factor is at its peak, at which stage the plant has also reached the maximum effective root depth, for supplying the necessary water requirement.
2.10 Weed control
Weeds that germinate early in the season (six to eight weeks after planting) compete with young cotton plants for space, water, sunlight and nutrients. Pre-emergence
herbicides can be used at the time of planting. The type of herbicide will depend upon the type of weed that holds the greatest threat (ARC, 2004).
Figure 2.5 Crop factors for cotton in different climatic regions
2.11 Harvesting
Cotton can be hand picked or harvested mechanically. Practically all the cotton produced in the USA is harvested by machine (Munro, 1987). Harvesting begins about six months after planting and is the most expensive operation of cotton cultivation. Cotton is picked as soon as the boll opens. If left in the field for a longer period it may fall out or be damaged by rain. Hand picking is continued over a period of two months or more because all the bolls do not ripen at the same time. It is desirable to pick dry cotton free from trash. In general, hand picking produces considerably cleaner cotton when compared with mechanical harvesting (Kochhar, 1981).
2.12 Quality and grading
New spinning technologies have an impact on cotton fiber properties and therefore there is an increasing need for finer, stronger, and cleaner cottons. The changing emphasis in fiber selection has already had, and will continue to have a far-reaching impact on breeding, farming, ginning, and merchandising cotton. Cotton is classed to determine the grade, staple and character which indicates to a large extend the spinning utility and hence the market value of each bale. There is three factors that determines grade, namely: Colour, leaf residue (impurities) and preparation (The degree of smoothness or coarseness of the cotton lint after ginning (Schröder, 2006). The High volume instrument is the established instrument for determining fibre quality for cotton. Measurements obtained by the USTER HVI Classing include: Length and length uniformity, strength and elongation, micronaire and maturity, color and trash, and short fiber index (Uster ® HVI Classing, 2004).
2.12.1 Lint Length.
Length and length uniformity are two of the most important cotton fiber properties. Without sufficient fiber length, a fine yarn count cannot be spinned. Fiber length should be distributed evenly to produce a yarn at a high level of production efficiency. This is why fibre length (or “staple length”) was established as one of the first parameters in the cotton supply chain, determining the value of cotton. Acceptable fibre lengths are 26.9 to 29+ (Uster ® HVI Classing, 2004).
2.12.2 Lint Strength
Cotton fibres need to have certain strength to withstand the strain put on them during the opening, cleaning, and spinning processes. Fibre strength and elongation are directly correlated to yarn strengths and elongation. Fibre strength is a parameter that is being recognized in buying and selling cotton worldwide. Acceptable strengths is > 27 g tex-1 (Uster ® HVI Classing, 2004)
2.12.3 Micronaire and maturity
In order to achieve a certain yarn count, a specific number of fibres are required per cross-section. The micronaire value, along with the fibre length, determines to a large extend what yarn can be spun from the cotton. Micronaire in combination with maturity has a strong effect on the dyeing ability of the yarn and fabric. Micronaire is also recognized as an important property in the international cotton trade. Acceptable micronaire values are 3.5 – 4.9 (Uster ® HVI Classing, 2004).
2.13 Factors affecting yield and quality
Shedding of squares or young bolls can have a detrimental affect on the yield of cotton. Dippenaar (1990b) describes that excessive shedding (35%) may be related to one or more of the following conditions:
Water. Any large fluctuation in the availability of soil water. Drought is the major
cause of abscission.
Light. Prolonged periods of overcast weather can increase shedding.
Temperature. Abnormally high temperatures and cold periods favour shedding. Mineral nutrition. Deficiency of any element will result in an abnormal amount of
shedding of squares and bolls and correcting the deficiency will reduce this loss.
Plant population. An increase in plant population will cause an increase in shedding
percentage. This indicates that besides root competition, shading may also play an important role in this regard.
Pests. Damage (puncturing followed by necrotic patches) done by insects can result
in shedding.
2.13.1 Environmental stresses
When plants are subjected to environmental stress conditions such as temperature extremes, drought, herbicide treatment or mineral deficiencies, the balance between the production of reactive oxygen species and the quenching activity of the
antioxidants is upset, often resulting in oxidative damage. Plants with high levels of antioxidants (constitutive or induced) have been reported to have greater resistance to this oxidative damage (Gossett et al, 1994). Growth rate of leaf area and internode length increased as temperature increased to 27 to 30°C, then decreased at higher temperatures (Reddy et al, 1997).
2.13.2 Water stress
Water stress adversely affects both yield and fibre quality of cotton and any improvement of water use efficiency (WUE) would be expected to partially reduce these adverse affects (Stiller et al, 2005). Water is one of the most important limiting factors in profitable cotton production (Whitaker et al, 2008). Water causes major variation in cotton yield (Gerik et al, 1994). Plant water stress during square formation and early flowering resulted in fewer bolls to reach maturity, but this detrimental affect is mitigated by the development of bigger bolls due to greater lint growth. Moisture stress during ripening of the cotton crop, advanced boll opening, increased lint and boll development and consequently enhanced yields (de Kock et al, 1990). Cotton is often exposed to drought, which adversely affects both yield and quality (Saranga et al, 1998). In South Africa, where drought is a severe problem, the tolerance of economically important crops to drought-stress is of great value. Six South African cultivars were evaluated for changes in protein profiles during osmotic stress. Drought-related protein synthesis was found in the cultivars Lido, Delta Pine, Acala 1517-70 and OR3, while drought-related proteins were not observed in the cultivars Selati and Letaba. It would appear that drought-related protein synthesis was cultivar specific (van der Mescht & Ronde, 1993). Drip irrigation can promote cotton yield and earliness (Chu et al, 1995). Any large fluctuation in the availability of soil water can result in increased shedding, and subsequently a decrease in yield (Dippenaar, 1990a).
2.13.3 Nutrient deficiencies
Cotton yields have greatly increased since 1935, because of better crop management and the use of improved cultivars. One major management factor that greatly impacts yield of cotton is nitrogen fertilization (Meredith et al, 1997). The mineral nutrition of cotton depends on both the cotton root’s ability to explore the soil, and on the soil’s ability to supply N, P and K nutrients. Cotton has an indeterminate growth habit and some sensitivity to adverse environmental conditions that can result in excess fruit abscission (Bisson et al, 1994).
2.13.4 Pests
Insects and diseases have a great effect on the rate of abscission and shedding. Directly after squares or bolls has been damaged by an insect, (even if only punctured, a necrotic patch forms, followed by abscission (Dippenaar, 1990a). Heliothis spp. is major pests in many cotton-producing countries of the world. Cotton breeders are attempting to develop cultivars that have useful levels of field resistance or tolerance to tobacco budworm (Jenkins & Mcarty, 1994). Young cotton crops host a range of insect pests, including thrips (Thysanoptera). Leaf distortion, reduced leaf area and plant height, and growth delay are often observed in thrips-damaged cotton and, in cases of severe infestation, loss of vegetative buds and branching after release of apical dominance have been reported. Because of these effects, thrips have the potential to reduce yield and delay the maturity of cotton crops (Sadras & Wilson, 1998). The nectariless and okra-leaf traits confer low levels of resistance in cotton
Gossypium hirsutum L., to pink bollworm, Pectinophora gossypiella (Wilson, 1989).
2.13.5 Growth hormones
Yield in cotton is often associated with the number of bolls produced per unit area. Boll retention is an important process that affects lint yield. Many biotic stresses have been reported to have a direct influence on boll retention. The concentration of
important plant growth substances such as IAA (Indole acictic acid) and ABA (absitic acid) must be maintained or supplied at critical levels if a boll is to be retained (Heitholt & Schmidt, 1994). As an indeterminate perennial, cotton is susceptible to excessive vegetative growth during conditions of high temperature, water supply and soil fertility. With more intensive crop management and higher yielding cotton varieties, the practice of early stress has been replaced with the use of a growth regulator to restrict excessive vegetative growth (Constable, 1994).
2.13.6 Variety
In South Africa, Bt-technology (Genetically Modified Cotton) has proved to be not only effective against the target pests, which are the African bollworms on cotton, but it is also beneficial to farmers in the form of a higher yield production and improved crop protection (Bennett-Nel, 2007). Quality of cotton is directly linked to price, which is indirectly linked to yield. By comparing fibre quality parameters (strength, length, length uniformity and micronaire) across different technology types, i.e. single gene introduction (Bt-cotton or RR-cotton) (Jordan & Wakelyn, 2003) found that fibre quality is just as likely to have been improved as not. In South Africa no significant differences in length and strength between Bt- and non-Bt-cotton under irrigated and rain-fed conditions, although the micronaire was found to be lower in both Bt- and non-Bt-cotton under rain fed conditions (Joubert et al, 2001). Joubert et
al (2001) cited by Bennett-Nel, 2007 found Gin out Turn (GOT) to be higher in the
case of Bt-cotton when compared to non-Bt-cotton. Fibre properties of Bt-cotton were found to be more acceptable than those of non-Bt-cotton during studies in South Africa performed in the 1999 to 2001 seasons (Joubert et al, 2001).
Braden & Smith (2004) found that breeding for long staple cultivars has been successful, resulting in lines that possess improved yield and fibre quality but without unduly delaying crop maturity. Over the years, breeders have selected earlier maturing cultivars so that growers could maximize early season moisture, avoid late season build-up of insects, optimise their opportunity to recover from in-season
stresses, and avoid crop damage due to inclement weather during the harvest season (Braden & Smith, 2004). Genetic diversity among cultivars reduces vulnerability of the crop to a disease or insect pathogen. In cotton, diversity is important for long-term improvement in lint yield and fibre quality (May et al, 1995). In trying to increase the yield of upland cotton, breeders have indirectly selected more for increases in harvest index than in photosynthesis. Future cotton yield advances may need increases in both harvest index plus photosynthesis (Pettigrew & Meredith, 1994). Previous research has shown that tropical accessions have useful genetic variability for insect and disease resistance and fibre quality (McCarthy et al, 1996). Cotton with alternative leaf morphologies, such as the cleft-shaped okra-leaf types, offers production advantages such as earlier maturity.
Cotton cultivars that mature early without sacrificing yield can reduce production costs (Heitholt & Meredith, 1998). The genetic improvement of cotton fibre quality and yield is imperative under the situation of increasing consumption and rapid development of textile technology. Previous researchers did identification of stress response genes expressed in cotton. Major stress factors in cotton included the wilt pathogens Verticillium dahliae, Fusarium oxysporum f. sp. vasinfectum, bacterial blight, root-knot nematode, drought, and salt stress. A few genes related to the biosynthesis of gossypol, other sesquiterpene phytoalexins and the major seed oil fatty acids were isolated from cotton (Liu & Zhang, 2008).
2.14 Breeding
2.14.1 Early breeding history in South Africa (1920 – 1990)
Breeding from as early as in the 1920’s were done in South Africa, where hairy cotton varieties were developed at Barberton and exploited for their resistance to leafhoppers. (Annecke & Moran, 1982).
In 1970 the South African textile industry favored an increase of fibre length and micronaire index of lint from certain areas. Emphasis later shifted to improvement of fibre tenacity, and with the increased importance of rotor spinning, a lower micronaire index became increasingly desirable (van Heerden et al, 1987).
Greeff (1986) explains that the breeding programme (1986) for Upland cotton in South Africa has evolved over a period of 77 years. It was done in four distinct breeding programmes located at Upington, Vaalharts, Loskop and Rustenburg. These programmes were co-coordinated from the TCRI (Tobacco and Cotton research Institute).
In many parts of the world, an important aim of cotton breeding is earliness of crop maturity. Subsequently the TCRI (Tobacco and Cotton Research Institute) initiated a breeding project in 1986 for the development of cotton cultivars adapted to a short growing season. The study investigated cultivar-environment interactions involving 15 short-season cultivars used in a programme at three different localities namely, Loskop, Vaalharts and Rustenburg (de Kock, 1994).
In the breeding programme of 1987, the cultivar Acala 1517-70 was considered the standard as far as fibre characteristics were concerned. Acala 1517-70 then produced a better quality fibre than the other cultivars grown in South Africa but had a low yield potential. In the Vaalharts and Loskop programmes improved yield and fibre properties equal to those of Acala 1517-70, were the breeding objectives. Resistance to Xanthomonas spp and Altenaria spp formed part of the screening process. In the Upington area, a prerequisite was resistance to Verticilium wilt, resistance to the physiological disorder called red leaf disease, and improvement of the spin ability of the locally grown OR3 (van Heerden et al, 1987).
According to van Heerden (1988b) the national breeding program of South Africa was carried out at Groblersdal, Vaalharts and Upington. Evaluation of breeding lines and cultivars in the three areas over various seasons supplied information of
importance to breeders, ginners and spinners. Van Heerden (1988b) states that preliminary results from breeding trials indicated a finer but more mature fibre at Vaalharts.
2.14.2 Breeding after 1990
The Agricultural Research Council undertook cotton breeding for yield and quality improvement, at the Institute for Industrial Crops (ARC-IIC), in the North-West Province. The Plant Breeding Division at the Institute was responsible for developing new cultivars that will produce more efficiently under existing or potential environmental conditions, through manipulation of gene frequencies (Swanepoel, 2004). This division had various programmes aimed at improving genotypic backgrounds for improved production in dry land conditions, irrigation conditions and short growing season conditions, resistance to verticilium wilt and nematodes. The germplasm consists of 1726 accessions.
Cornellissen (2002) describes a program to develop jassid resistant varieties through incorporation of hairiness to adapted cultivars or breeding lines to address the problems of limited resource farmers in the Republic of South Africa.
CHAPTER 3
MATERIALS AND METHODS
3.1 Trial sites
Trials to evaluate the performance of a number of cotton cultivars under irrigation were conducted at Loskop, Makhathini, Rustenburg, Upington, Vaalharts and Weipe (Figure 3.1). These sites are representative of production areas 1 to 8, namely:
Area 1: the Lower Orange River area (irrigation). Area 2: Griqualand West (irrigation).
Area 3: North-West, Vryburg. Area 4: North-West, Rustenburg.
Area 5: the Limpopo Valley (irrigation). Area 6: Loskop - Springbok Flats. Area 7: Mpumalanga (irrigation). Area 8: KwaZulu- Natal.
3.2 General trial procedure
At each trial site the trial was planted on a soil type that was representative of the soils on which cotton is produced in that area (Table 3.1). Conventional soil preparation practices were followed, and fertilizers were applied according to the soil analysis and the yield potential for each site.
CottonSA recommended all the cultivars for planting during the 2003 to 2006 seasons, in the different cotton producing areas of South Africa. The two imported cultivars that were evaluated in the trials are from Zimbabwe and are long staple cultivars with longer fibres. Spinners need more uniform fibre, and therefore cotton cultivars decreased during the past decade.
The following five cultivars were evaluated using a randomized complete-block trial design, replicated three times, at each site, namely:
DeltaOPAL - a conventional cultivar from Delta Pine. This was used as the control treatment against which the others were evaluated:
NuOPAL - a cultivar from Delta Pine containing the Bollgard™ gene; DeltaOpal RR - a Delta Pine cultivar containing the Roundup Ready™ gene; SZ9314 and LS219 - two cultivars from Quton Cotton in Zimbabwe.
Figure 3.1 Localities in the different irrigated cotton-production areas in South Africa, showing trial sites
Plots were 4 x 9 m in size and contained four rows spaced 1 m apart, with plants spaced 0.15 m apart in the row. Two seeds were planted by hand at each planting station and the seedlings were thinned out to a single plant per station when they were approximately 15 cm tall. Thinning was completed within three weeks of emergence. This resulted in a plant population of 70 000 plants ha-1, the recommended plant population for cotton under irrigation. Data were collected from a net plot of 2 x 8.7
m. Only the two centre rows were harvested and the first and last plants from those rows were excluded to eliminate side effects.
3.3 Fertilization
Fertilizer was applied according to the soil analysis done for each site (Tables 3.7, 3.9, 3.11, 3.13 and 3.15) and the yield potentials at each site. The fertilizer (N, P, K) application rates to achieve optimum yields at each site are given in Table 3.1. At Loskop, N was given in the form of LAN (28), P as Superphosphate (10.5) and K as K2SO4. Fertilizer at Makhathini was applied in the form of 2:3:4 (33) at planting and
two top dressing applications of LAN (28) at 4 and 8 weeks after planting. At Rustenburg, fertilizers were applied in the form of 2:3:4 (33) at planting and two LAN (28) top dressings at 4 and 8 weeks after planting. At Upington, fertilizer was applied in the form of 2:3:4 (30) at planting and two ASN top dressings were applied at 4 and 8 weeks after planting. At Vaalharts, fertilizer was applied in the form of 2:3:4 (33) at planting and three top dressing applications of LAN (28) at 4, 7 and 9 weeks. At Weipe the farmer gave 70 kg ha-1 N and no P and K (Table 3.2).
Table 3.1 The different amounts of nutrients required by the aboveground parts of the cotton plant for the production of different yields
Seed cotton yield N P K
(kg ha-1) (kg ha-1) 1000 90 15 60 1500 140 18 65 2000 180 20 70 2500 215 28 85 3000 230 30 100 3500 240 30 115 4000 245 30 130 4500 250 30 140 Source: ARC, 2004.
3.4 Irrigation
The cotton was irrigated accordingly to the water requirements of the crop. Irrigation was applied via overhead irrigation, at all sites, with the exception of Weipe, where drip irrigation was used.
Table 3.2 Soil form, fertilization amounts and rainfall during different seasons at different localities
Locality Season Soil form* Fertilization (kg ha-1)
N P K Rainfall (mm) Loskop 2003/2004 Hutton 140 70 40 134.7 2004/2005 Hutton 140 70 40 315.8 2005/2006 Hutton 140 70 40 436.1 Makhathini 2003/2004 Hutton 150 40 80 275.2 2004/2005 Hutton 150 40 80 585.2 2005/2006 Hutton 150 40 80 401.8 Rustenburg 2003/2004 Arcadia 140 30 80 710.8 2004/2005 Arcadia 170 30 80 513.4 2005/2006 Arcadia 150 30 80 636.3 Upington 2003/2004 Hutton 150 30 40 303.1 2004/2005 Hutton 150 30 40 196.1 2005/2006 Hutton 150 30 40 356.8 Vaalharts 2003/2004 Hutton 220 50 70 334.8 2004/2005 Hutton 220 50 70 295.7 2005/2006 Hutton 260 50 70 212.3 Weipe 2003/2004 Hutton 70 0 0 295.4 2004/2005 Hutton 70 0 0 165.9 2005/2006 Hutton 70 0 0 93.1 * Grond klassifikasie, 1977 3.5 Weed control
Weed control practices differed between the various sites depending on the weed spectrum that was found. Both monocotyledonous (grasses and sedges), and broadleaf weeds were controlled by pre- and post emergence herbicides. The
(Directorate of Agricultural Information, 1988). Hand hoeing was also done to keep trials weed free for the duration of the season.
Table 3.3 Herbicides used to control weeds at the various trial sites
Site Chemical application
Active ingredient Concentration (g ℓ-1) Application rate Time of application
Loskop Trifluralin 480 1.5 ℓha-1 Pre-emergence
Rustenburg S-metolachlor Fluometuron / prometryn 915 250/250 4.0 ℓha-1 1.3 ℓha-1 Pre-emergence Pre-emergence Makhathini S-metolachlor Fluometuron / prometryn 915 250/250 3.0 ℓha-1 0.6 ℓha-1 Pre-emergence Pre-emergence
Vaalharts Trifluralin 480 1.0 - 1.5 ℓha-1 Pre-emergence
Upington Glyphosate MSMA 360 720 300 mℓ/15 ℓ H2O 375 mℓ/15 ℓ H2O Post-emergence Post-emergence Weipe S-metolachlor Fluometuron / prometryn 915 250/250 0.6 ℓha-1 3.0 ℓha-1 Pre-emergence Pre-emergence 3.6 Insect control
Cotton fields were scouted for insects in such a way that the observations were representative of the specific field. A minimum sample of 24 plants were randomly chosen in each plot and investigated for pests, except for spider mite that requires a sample of 48 plants. The whole plant including the young bolls and squares should be examined. Control thresholds for important cotton pests are summarized in Table 3.4. Pesticides applied at the different localities are summarized in Tables 3.6, 3.8, 3.10, 3. 12, 3.14 and 3.16.
3.7 Harvesting and measurements
Defoliation was left to occur naturally and no chemical defoliation was done on the trials. All harvesting was carried out by hand to ensure that the different treatments was harvested and weighed accurately. The first harvest at all the localities was carried out at the beginning of April when approximately 60 - 70 % of the bolls were
opened. The remainder of the cotton was picked during the first or second week of May, depending on the trial site.
After harvesting, the following yield and quality parameters were determined:
a) Yield
• Total seed cotton yield (kg ha-1)
• Fibre percentage (fibre was removed from seeds with a mini gin) • Fibre yield (kg ha-1)
b) Quality
The fibre laboratory at Cotton SA, Pretoria, determined fibre qualities. • Average fibre length (mm)
• Fibre strength (g tex-1) • Micronaire (Fibre fineness)
3.8 Statistical analysis
After collection, the data were subjected to statistical analysis using the GenStat® (Payne et al., 2007) statistical program. Treatment means that were significant at the 5% level of significance were separated using Tukey’s Least Significant Difference test (LSDT) as described by Snedecor (1980). AMMI analysis was done using the
GenStat® AMMI procedure. The Additive Main effects and Multiplicative Interaction, or AMMI, technique is primarily used for exploring cultivar x environment data.
Table 3.4 Control thresholds for important cotton pests (ARC, 2004)
Pest Control threshold
Conventional + herbicide tolerant
Control threshold Bollworm resistant cotton American bollworm Red bollworm Spiny bollworm Bollworm complex 5 larvae / 24 plants
6 eggs / 24 plants or 2 larvae / 24 plants
2 larvae / 24 plants
5 larvae / 24 plants
More than 5 plants with one or more bollworm / 24 plants
More than 2 plants with one or more red bollworm / 24 plants
More than 2 plants with one or more spiny bollworm/ 24 plants
More than 5 plants with one or more bollworm / 24 plants
Spider mite When mites appear in localized spots, apply control to these spots only. When mites are distributed throughout the block, apply a blanket spray when the following thresholds are reached. Up to week 10: 0,5:
From week 11: Add 0,125 to 0,5 for each week after week 10. Control must be aimed at keeping the mite population below the threshold, until first boll burst or until 20 weeks after plant emergence
Same as for conventional cotton
Aphids Control when honeydew is found on plants Same as for conventional cotton Whitefly Control as soon as 10 whiteflies / leaf are
found or when leaf edges turn yellow and curl around
Same as for conventional cotton
Leafhoppers Control when 2 leafhoppers per leaf are found or when leaf edges turn yellow and turn around
Control when 3 or more leafhoppers per plant are found.
Thrips Control only when leaf damage occurs early in the season
Stainers Control as soon as the first colonies appear Control when 6 or more colonies are found per 24 plants
Table 3.5 Soil analysis during the 2003 to 2006 seasons at Loskop Description 2003/2004 2004/2005 2005/2006 pH 6.15 6.9 6.23 Resistance 389 415 538 mg kg-1 N 12 3 3 P 10 6 5 K 219 214 205 Ca 1397 1903 1360 Mg 693 879 699 Na 60 81 34 S-values 13.5 17.7 13.3 Ca % 51.6 53.6 51.4 Mg % 42.2 40.8 43.3 K % 4.2 3.6 4.1 Na % 1.9 1.9 1.2 % Sand % Loam % Clay 54 9 37 57 7 36 56 8 36
Table 3.6 Insect control during the 2003 to 2006 seasons at Loskop
Season Pest Product Times
applied
Application rate
2003/2004 Bollworms Endosulfan 7 1 litre ha-1
Cypermethrin 7 75 ml ha-1
Jassids Acetamiprid 3 50 g ha-1
Red Spider Mite Abamectin 2 300 ml ha-1
Mineral oil 2 2 litres ha-1
2004/2005 Bollworms Endosulfan 7 1 litre ha-1
Cypermethrin 7 75 ml ha-1
Jassids Acetamiprid 4 50 g ha-1
Red Spider Mite Abamectin 2 300 ml ha-1
Mineral oil 2 2 litres ha-1
2005/2006 Bollworms Endosulfan 9 1 litre ha-1
Alpha-cypermethrin
9 75 ml ha-1
Jassids Acetamiprid 4 50 g ha-1
Red Spider Mite Abamectin 2 300 ml ha-1
Mineral oil 1 2 litres ha-1
Table 3.7 Soil analysis during the 2003 to 2006 seasons at Makhathini Description 2003/2004 2004/2005 2005/2006 pH 6.62 6.93 5.5 Resistance 669 600 968 mg kg-1 N 6 7 9 P 29 30 24 K 400 510 304 Ca 838 1445 476 Mg 268 388 158 Na 83 108 53 S-values 7.8 12.2 4.68 Ca % 53.8 59.4 50.6 Mg % 28.4 26.1 27.8 K % 13.2 10.8 16.6 Na % 4.7 3.8 4.95 % Sand % Loam % Clay 58 10 32 58 11 31 55 10 35 Table 3.8 Insect control during the 2003 to 2006 seasons at Makhathini
Season Pest Product Times
applied
Application rate
2003/2004 Bollworms, Aphids, Red
spider mite
Decis 3 200 ml ha-1
Mospilan 1 75 gr ha-1
Abamectin 1 400 ml ha-1
2004/2005 Bollworms, Aphids, Red
spider mite
Decis 3 200 ml ha-1
Mospilan 1 75 gr ha-1
Abamectin 1 400 ml ha-1
2005/2006 Bollworms, Aphids, Red
spider mite
Decis 3 200 ml ha-1
Mospilan 1 75 gr ha-1
